Metre gauge is the system of narrow gauge railways and tramways with a track gauge of 1,000 mm (3 ft 33⁄8 in). It has installations of around 95,000 kilometres (59,000 mi) in the world. It is the main gauge in some countries. In Europe large metre gauge networks remain in continuous use in Switzerland, northern Spain and for many European urban trams, although most metre gauge local railways in France, Germany, and Belgium closed down in the mid 20th century. With the revival of urban rail transport, in some cities metre gauge light metros were established, while in other cities metre gauge was replaced by standard gauge.

4,000 km (2,500 mi) in 2014. The length was 24,158 km (15,011 mi) in 1951 rising to about 30,000 km (19,000 mi) in 1991 and has decreased considerably since then as metre gauge is being converted to Indian gauge of 1,676 mm (5 ft 6 in) under Project Unigauge that began in 1991. Indian Railways is converting all metre gauge tracks to 1676mm gauge except heritage railways like Nilgiri Mountain Railway.